1. Field of The Invention
The present invention relates to a hydraulic machine that has a wheel supported by a shaft, said wheel and said shaft being mounted to move in rotation about an axis. The wheel of such a machine is designed to have a forced flow of water pass therethrough. Such a forced flow is a driving flow when the machine operates as a turbine. Such a flow is a driven flow when the machine operates as a pump.
2. Brief Description of the Related Art
In such a machine, a radial hydrostatic bearing can be provided around the shaft, with the function of taking up the radial forces to which said shaft is subjected. Such a bearing can be provided around an upper portion, around a lower portion, or around an intermediate portion of the shaft. It is known that a hydrostatic bearing can be equipped with an expansion seal, e.g. an inflatable seal, that makes it possible to protect the bearing from rising polluted water when the machine and the system for feeding water to the bearing are shut down. Such an inflatable seal is expanded during shutdowns of the machine, so as to isolate the bearing from its environment. Under normal operating conditions, the flow rate of water brought to the bearing is removed via the top and via the bottom of the bearing, thereby making it possible to procure both lift for the bearing and also removal of the energy dissipated by fluid friction, by generating of a continuous film of water. In the event that an inflation seal remains jammed in the expanded configuration, the water in the bearing cannot be removed towards the bottom of the bearing, which disturbs the flow of the water and the operation of the bearing. The lift of the bearing is reduced and the water that is held captive in the lower portion of the bearing tends to heat up, with a risk of the film of water being totally or partially transformed into steam, and a risk of the shaft coming into contact with the stationary bushing of the bearing.
These problems can also arise with a bearing that is not provided with an inflatable seal and in which removal of water from the bearing is obstructed, upwards or downwards, by any other obstacle.
Analogous problems can arise with horizontal-axis machines, which machines can also be equipped with hydrostatic or hydrodynamic seals.
It is also known, from U.S. Pat. No. 4,071,303, to provide the outside surface of a pump rotor with recesses for feeding a water bearing. Those recesses are connected to the upper edge and to the lower edge of the rotor via channels for removing solid bodies that could penetrate into the recesses. In the event that the bearing is obstructed, in the upper portion or in the lower portion, the film of water that makes up the bearing cannot be removed and might be transformed into steam, thereby limiting the lift of the bearing or reducing said lift to zero.